AR barrel throat depth

[LRRPF52]

Make a load ladder at the bottom of the load spectrum working up with the bullet jammed into the lands - my gun seems to like 0.025". You may see pressure sooner than without jamming into the lands, but I went up to 32 grains of CFE223 under a 123, had a wildly compressed powder charge, and jammed 0.025" and still had no pressure signs. My good load with cfe223 is currently 29.8grains IIRC, COAL is 2.245" or something analogous to that. That particular load is about 1.5 minutes lower at 625 yards than Hornady BLACK, so it is moving a tad bit slower.

(The main reason I cant remember the COAL is because I use the ogive gauge that hornady sells - as someone else mentioned, seating to a specific case head to ogive length is far more consistent than COAL.)

I do not recommend jamming the lands in a gas gun because you will have a very hard time extracting them if you don't get to fire. You are also not allowing the jump with start pressure transition into the lands, so pressures can spike on you, especially from the small volume case of the 6.5 Grendel and its efficient 30˚ shoulder.